study of blended wing body design (bwb

STUDY OF BLENDED WING

BODY DESIGN (BWB)

Presented by :Chirag.D.Soni

1MJ09MAE03

Contents

1. Introduction to BWB aircraft configuration

2. History of BWB

3. How is it different from flying wing designs

4. Square-Cube-Law

5. Basic configuration and nomenclature of Boeing BWB 450

6. Flying wing challenges

7. What Does the Future Hold for the BWB?

8. Preliminary sizing

9. Aero disciplines: Structures

Aerodynamics

Flight mechanics

Ground handling

10. BWB advantages compared to today's advanced aircraft

11. Stealth configuration in military aircrafts

MVJ College department of Aeronautics

Introductionto BWB aircraft

configuration

Classification


1) Conventional Configuration: "Tube and Wing" or "Tail Aft"

2) Blended Wing Body (BWB)

3) Hybrid Flying Wing

4) Flying Wing

5) The Boeing C wing

BWB Definition


The Blended Wing Body aircraft is a blend of

the tail aft and the flying wing configurations.

A wide lift producing centre body housing the payload

blends into conventional outer wings

What is a Blended wing body concept ?


Blended Wing Body, or BWB, designates an

alternative airframe design which incorporates

design features from both a futuristic fuselage

and flying wing design. The purported

advantages of the BWB approach are

efficient high-lift wings and a wide airfoil-

shaped body. This enables the entire craft to

contribute to lift generation with the result of

potentially increased fuel economy.

The airplane concept blends the fuselage,

wing, and the engines into a single lifting

surface, allowing the aerodynamic efficiency

to be maximized

How is it different from flying wing

designs


Flying wing designs are defined as having

two separate bodies and only a single wing,

though there may be structures protruding

from the wing.

Blended wing/body aircraft have a

flattened and airfoil shaped body, which

produces most of the lift to keep itself aloft,

and distinct and separate wing structures,

though the wings are smoothly blended in

with the body.

History of BWB

The following provides an insight into the aircraft design evolution. A flying wing is a type

of tail-less aircraft design and has been known since the early days of aviation. Since a wing

is necessary for any aircraft, removing everything else, like the tail and the fuselage, results in

a design with the lowest possible drag. Successful applications of this configuration are for

example the H-09 and latter H-0229 developed by the Horton brothers for Nazi’s during

1942. Latter Northrop started designing flying such as NIM in 1942 then latter XB-35

bomber that flew first in 1946, and the stealthy B-2 bomber that flew first in 1989.

In modern era after B-2 bomber blended wing body was used for stealth operations. The

unmanned combat aerial vehicle (UCAV) in the year 2003 X-47 was subjected to test flights.

Flight tests began on July 20, 2007 - the first flight reached an altitude of 7,500 feet MSL

(2,286 m) and lasted 31 minutes. The remotely-piloted aircraft was successfully stalled for the

first time on 4 September, with fixed leading edge slats, a forward center of gravity, and 23-

degree angle of attack (2° beyond the maximum coefficient of lift ). Stall testing was

repeated on 11 September with a NASA pilot at the console. NASA and Boeing successfully

completed initial flight testing of the Boeing X-48B on March 19 2010.

The Blended Wing Body (BWB) is a relatively new aircraft concept that has potential use as

a commercial or military transport aircraft, cargo delivery or as fuel tanker


1946 XB-35 bomber

YB-49 1949 B-2 bomber 1989 X-47A (UCAV) 2003

X-48 B 2007

H09 1939

H229 1942

Team members studying the Blended-Wing-

Body (BWB) design

McDonnell Douglas,

Stanford University,

The University of Southern California,

Clark Atlanta University,

The University of Florida,

NASA Langley and Lewis Research Centers.

Boeing Phantom Works

Air Force Research Laboratory

NASA's Dryden Flight Research Center

Institute of Aircraft Design and Lightweight Structures, TU Braunschweig


Square-Cube-Law


When a physical object maintains the same density and is scaled up, its mass is increased by the cube of the

multiplier while its surface area only increases by the square of said multiplier. This would mean that when

the larger version of the object is accelerated at the same rate as the original, more pressure would be exerted

on the surface of the larger object.

Basic configuration and nomenclature of

Boeing BWB 450


BWB-450 specifications

Seating capacity 478 passengers in three class interior arrangement

Design Range 7750 nautical miles

No: of engines The BWB-450 uses three upper surface pylon mounted turbofan engines,

located at the trailing edge of the wing, for propulsion

Type of engines 3 UEET direct drive turbofan engines (Ultra-Efficient Engine Technology)

Cruise mach no: A recent Boeing optimization study1 indicated that a cruise Mach number

of 0.90 is optimal for a range of 7,750 nm.

Maximum gross weight 823,000 lb

Cruise speed 0.85 mach (560 mph)


Flying wing challenges

1. Cabin pressurization is one of several design challenges facing the BWB.

2. Current airliners have a cigar-shaped fuselage ideal for maintaining cabin pressurization.

3. The BWB, however, has a unique shape that requires a novel approach to satisfy

pressurization and structural needs.

4. The design uses ten intermediate chord-wise (front-to-back) ribs to connect the upper and

lower wing skins. These ribs separate the interior into ten passenger bays.

5. Advanced composite material will be required to minimize the amount of structure needed to

withstand the pressurization loads and deflections in the skins.

6. Open certification problems : unstable configuration , ditching

7. Open design problems : rotation on take-off, landing gear integration,


What Does the Future Hold for the BWB?



Clearly the BWB shows a significant advantage over a conventional aircraft in terms

of performance and weight. However, the BWB is a revolutionary aircraft concept

and will require a large and expensive engineering effort to become a reality. Most

likely, before being used as a transport aircraft, it will be utilized for military

applications. In fact, Boeing and the US military are designing the BWB to be used

as an advanced tactical transport and as an air refuel tanker (Figure 10). The BWB

has a large fuselage and can carry massive amounts of fuel. Also, it can provide two

permanent refueling boom stations, rather than one as in the KC-135, KC-10 or KC-

767.

Figure 10: A Boeing BWB tanker

with pylon-mounted engines

(picture from Boeing).

Other BWB projects 5th Framework Program of the

European Commission: VELA and MOB


VELA 1 VELA 2

Very Efficient Large Aircraft (VELA) from 1999 to 2002

6th Framework Program of the European Commission:

(VELA follow on)


Vela 3 (2003-2006)

X48-b first flight July 20, 2007

Flight tests began on July 20, 2007 - the first flight reached an altitude of 7,500 feet MSL

(2,286 m) and lasted 31 minutes. The remotely-piloted aircraft was successfully stalled for

the first time on 4 September, with fixed leading edge slats, a forward center of gravity, and

23-degree angle of attack (2 beyond the maximum coefficient of lift). Stall testing was

repeated on 11 September with a NASA pilot at the console . NASA and Boeing

successfully completed initial flight testing of the Boeing X-48B on March 19 2010.

http://en.wikipedia.org/wiki/Stall_%28flight%29

http://en.wikipedia.org/wiki/Leading_edge_slats





http://en.wikipedia.org/wiki/Center_of_gravity





http://en.wikipedia.org/wiki/Angle_of_attack





http://en.wikipedia.org/wiki/Coefficient_of_lift





Design cycle


In order to investigate potential

improvements and to predict major

design challenges of this new class of

aircraft the modeling and analysis

capabilities of the in-house aircraft

design tool of the Institute of Aircraft

Design and Lightweight Structures,

TU Braunschweig (IFL), PrADO,

have been adapted to the BWB

requirements

The methods used and the modeling

and analysis capabilities of the

improved, BWB-specific PrADO-

system are described.

Preliminary sizing


• Data collection

• Preliminary Weight estimation

• Optimization of wing loading and thrust

loading

• Wing design

• C.G calculation

• Control surface design

• Features of designed airplane

• Details of performance estimation

Preliminary multidisciplinary aircraft design

with the tool PrADO


1. Design requirements of the configuration are summarized and completed.

2. Aircraft geometry is calculated based on the parametric aircraft description (see Section 3.2).

3. An aerodynamic panel model of the airplane is created, and maps of aerodynamic coefficients are generated for the whole

flight regime

4. A propulsion sizing and engine characteristics calculation is performed. A thermodynamic cycle model is used to size the

turbo-fan engines including a geometry and mass estimation—based on the latest thrust requirements

5. Flight mission simulations are undertaken to create performance data and to determine the required fuel masses for

prescribed missions

6. The structural sizing module (SSM) includes a multi-model generator (MMG) that creates a structural model (finite

element model) and an aerodynamic surface panel model simultaneously.

7. Component masses for systems and primary and secondary structures are calculated. Structural mass is based on the sized

finite element model with additional corrections to account for sealants, paints, and other omitted details of the FE mode

8. Direct operational costs (DOC) are calculated for the life-cycle of the aircraft based on economical data, aircraft masses,

and performance data

9. Satisfaction of design boundaries (e.g., compliance with take-off and landing distances) is controlled, and the consistency

of the database is checked

Structures


Aerodynamics


One of the beauties inherent in a BWB airliner is it strength. It

readily absorbs both cabin pressure and wing bending loads, and

in recent tests in the Stanford University wind tunnel, a 6% scale

model easily passed all extreme flight envelope tests.

The BWB concept reduces the load on the outboard wing section

airfoils, while the large centerbody chord provides enormous

strength, requiring a much low sectional lift coefficient. This

reduced lift demand allows the large thick profile of the

centerbody to hold passengers and cargo, without exacting a high

compressibility drag penalty. Due to its shape and structure,

typical shocks evident on the thinner outboard wing panels

become very weak on the centerbody. Ahead of this shock,

airflow is supersonic; behind it, the air slows and that sub-sonic

area is highly suitable for engine installation. The low effective

wing loading of the BWB and its beneficial trim effect means that

no exotic high lift system is necessary; only leading edge slats are

necessary on the outboard wing, with all trailing edge devices

made up of simple hinged flaps which double as elevons.

Wake Turbulence


Flight Mechanics


Placing the engine


The BWB program is examining a new method

for engine installation that promises to increase safety

and fuel efficiency. Three advanced “high-bypass

ratio” engines will be buried in the trailing edge of

the center section of the BWB wing. While conventional

aircraft engines only take in “free-stream air,”

both the air on and near the surface of the wing will

flow through the BWB’s curved inlets and into its

engines. Taking in the layer of air on the wing surface

reduces drag. While this technology will require

validation before becoming a reality, researchers are

initiating tests to determine acceptable levels of

turbulence in the engine inlet.

Ground Handling (vela 3)


A cargo loading vehicle drives in between.

Cargo loading from below with lifting system. Catering from the right.

Water / waste servicing on trailing edge left side.

Ground Handling

BWB advantages compared to today's

advanced aircraft


better L/D 10 to 15% better

reduction in emissions yes

reduction in noise only with engines on top (reduction in noise to 42db below

stage 4)

increase of airport capacity yes, more than 750 pax per A/C

(probably no problems with wake turbulence)

Fuel burnt when compared to

conventional aircraft

20% less

Stealth configuration in B2 bomber


There is no point in considering military aerodynamic

configuration development without including stealth. It

plays a key role in the configuration layout.. Although

the details are classified, certain basic principles have

been described. Stealth is usually considered to consist

of several elements (often referred to as signatures):

• radar cross section, rcs • infrared

• visual • aural

Jack Northrop who

established the northrop

corporation along with

Donald Douglas to develop

first the YB-49 and latter the

B-2 stealth Bomber


How rcs works

(1) A radar site transmits a signal and measures the signal that is returned from the target

(in this case an airplane). When the sending and receiving antennas are co-located, the

radar is known as monostatic. This is the usual case. If the receiving antenna is located

somewhere else, the radar is bistatic. Bistatic systems may be able to detect aircraft

designed to operate stealthily against monostatic systems. This is a fundamental

consideration in stealth.


B-2 bomber specifications

Crew: 2

Length: 69 ft (21.0 m)

Wingspan : 172 ft (52.4 m)

Height: 17 ft (5.18 m)

Wing area: 5,140 ft² (478 m²)

Empty weight: 158,000 lb (71,700 kg)

Loaded weight: 336,500 lb (152,200 kg)

Max take off weight : 376,000 lb (170,600 kg)

Powerplant: 4× general electric f111-GE100

non- afterburning turbaofans , 17,300 lbf (77 kN)

each

What makes B-2 bomber a stealth configuration

It continuously changes shape when looked from different to confuse radar

Whatever beams are locked onto it are either get reflected in outer space or

reduced or dissipated into nothing

Coated with special RAM (radar absorbing material ) such as carbon fiber

composite and top secret reflective paint to reduce detection from enemy.

Electronic counter measure for jamming radar makes it undetectable

aircraft.

RCS (radar cross section ) is 1000 times less then B-52 bomber

It has special exhaust vents on top of which when hot gases are mixed with

cooler air make it almost undetectable to heat seeking SAM(surface to air

missile )



Thank you

study of blended wing body design (bwb

Documents